The invention concerns an actuation system for a hydraulically operable elevator and a test method to check the integrity of an actuation system.
Normally aircraft elevators whose inclination can be altered relative to the longitudinal alignment of an aircraft fuselage are trimmed, i.e. altered in their inclination relative to the aircraft fuselage, using trapezoidal thread screws or recirculating ball screws. Since very high demands are placed on trimming actuators of this kind with regard to their reliability, i.e. probability of failure, two load paths must be provided in most cases, implemented in terms of a spindle with an internal second load path and a duplicated connection to the structure. However, this results in a design that is relatively complex in mechanical terms. Elevator actuation systems with trimming spindles with an internal second load path cannot be monitored fully automatically as regards their structural integrity. Furthermore actuation systems of this kind have internal free play as a result of their structural joints, which can lead to undesirable aeroelastic effects and impairment of passenger comfort.
In general actuation systems with spindles are the cause of a relatively large maintenance activity and hide the risk of a mechanical seizure of the actuation system.
DE 10 2005 042 511 A1 discloses a trim actuator operating system comprising a hydraulic linear actuator, a blocking device for blocking the actuator and two hydraulic systems for operating the actuator.
EP 1 721 825 A1 describes a flight control surface actuation system with two actuator devices. One of the actuator devices is realized by an electro-mechanical actuator which can be blocked by a locking device.
From DE 10 2004 047008 A1 a drive solution with two parallel, mechanically synchronised spindles, is of known art.
In DE 10 2005 042 511 A1 an hydraulic simplex elevator drive with power supply redundancy and mechanical locking is described. With this drive concept a high degree of fault tolerance and satisfaction of high availability requirements is only achieved in a very limited manner, or in fact not at all. Because of the simple form of structural joint this drive also has internal free play.